Ultrasound of Temporal and Axillary Arteries in Giant Cell Arteritis: Halo Sign and Compression Test

Clinical Context

Giant cell arteritis (GCA) is considered a systemic vascular disease (Tato F, Hoffmann U. Giant cell arteritis: a systemic vascular disease. Vasc Med. 2008). Ultrasound evaluation of large vessels in vasculitides is described in the literature as a tool for visualizing vessel wall involvement (Lai K-L et al. Ultrasonography of Large-Vessel Vasculitides. J Med Ultrasound 2012).

Halo Sign

The provided source excerpts do not contain a detailed description of the halo sign with specific quantitative criteria and wall thickness threshold values — [clarification needed from primary sources]. General principles of peripheral arterial examination using color and spectral Doppler are governed by the ACR-AIUM-SRU Practice Parameter (Practice Parameter for the Performance of Peripheral Arterial Ultrasound Using Color and Spectral Doppler, 2025).

Compression Test

The specific methodology of the compression test in GCA (compression sign) is not described in the available source excerpts — [clarification needed]. In general recommendations for vascular ultrasound, compressibility assessment is applied predominantly to veins and in suspected vascular compression syndromes (Diagnostic Ultrasound: Musculoskeletal, 2025).

Technical Aspects of Scanning

For vascular studies, including the subclavian/axillary region, correct Doppler settings are important. According to general recommendations for arterial examination, the insonation angle should not exceed 60°, as this reduces the sensitivity of Doppler and color signals; the Doppler gate is positioned in the center of the artery—in the zone of peak flow velocity (Diagnostic Ultrasound: Musculoskeletal, 2025). Artifacts should be considered: mirror artifact from the pleura when scanning the subclavian artery and acoustic shadowing from calcified plaque (Textbook of Diagnostic Sonography, 2023).

Contrast Enhancement (CEUS)

The application of contrast-enhanced ultrasound for assessment of carotid artery wall in patients with Takayasu arteritis or giant cell arteritis is reflected in EFSUMB guidelines on CEUS for non-hepatic applications (Schinkel AFL et al. Eur Heart J Cardiovasc Imaging 2014; Possemato N et al. Rheumatology 2014).

Limitations

Detailed diagnostic criteria (halo thickness, thresholds, compression test positivity) and the names of corresponding consensus documents are absent from the provided excerpts and require clarification from specialized recommendations [clarification needed].